Design and Performance of an Indigenous Water Recirculating Aquaculture System for Intensive Production of Nile Tilapia, Oreochromis niloticus (L.), in Saudi Arabia

Yousef S. Al-Hafedh and Aftab Alam*
Volume 8, June 2007

*Corresponding Author

Keywords: tilapia, recycling, biofilter, waste, Saudi Arabia, nitrification

Footnote
International Journal of Recirculating Aquaculture 8 (2007). All Rights Reserved
© Copyright 2006 by Virginia Tech and Virginia Sea Grant, Blacksburg, VA USA

ABSTRACT

Increasing demand for fish and scarcity of fresh water press the need to adapt new technologies of intensive water recirculating aquaculture in Saudi Arabia to maximize water recycling and increase fish production. A commercial scale recirculating aquaculture system was developed in triplicate using locally available materials to produce Nile tilapia. The system was operated to produce more than 50 kg fish/m3/cycle and its filters were evaluated for their efficiency in organic waste removal from the effluents. Each replicate had a culture tank, two mechanical filters with sand/gravel medium, two submerged biofilters with plastic media, a sump and two pumps. Mixed sex Nile tilapia at a density of 188 fish/m3 and size of 76.4 g were stocked and fed a 34% protein diet at 3% body weight per day (initially). Water temperature was maintained at 28±1șC, water flow rate was adjusted to 300 liter/min and the culture tank and biofilter were aerated. Water samples were collected from the inlet and outlet of each component and were analyzed for important parameters. Values (±SE) of total ammonia nitrogen (TAN) (0.98±0.1 ppm) and nitrite-nitrogen (NO2-N) (0.48±0.02 ppm) in the fish culture tanks were within the acceptable limits, while the other water quality parameters were also maintained under normal range by the filtration system. Removal rates (±SE) of 186.7±31.59 g TAN/m3/day and 66.53±16.9 g NO2-N/m3/day, respectively as well as TAN and NO2-N removal efficiencies (31.45±2.32% and 21.05±3.8%, respectively) were measured across the PVC biofilter medium. The area specific TAN and NO2-N removal rates (±SE) or nitrification rates (0.34±0.06 g/m2/day and 0.15±0.05 g/m2/day) for the biofilter were comparable with the performance of other commercial intensive recirculation systems. Mean final weight (±SE), final biomass, growth rate, SGR, FCR, and percent survival for the mixed-sex tilapia was 277.21 (1.76) g/fish, 50.21 kg/m3, 1.34 g/fish/day, 0.86%, 1.89, and 96.53%, respectively whereas the average water use was 0.4 m3/kg of fish production. Locally available materials were found to be appropriate media for solid and organic waste removal. More than 85% of the system water volume could be recycled daily while fish production per unit space was also multiplied to 3-6 folds compared to the traditional culture practice.